198 CRUSTACEA* 



foot-jaws are foliaceous. It is of a rod colour, and was discovered by 

 Sir Joseph Banks in his voyage round tlie world. It collected in 

 such immense numbers that the Ocean seemed to be of one blood-red 

 colour. 



The JErjlea, Id., is only distinguished from the i)receding genus, 

 and from Galathea, by the dentation of the mandibles, by tlie second 

 joint of the external foot-jaws being shorter than the first, and by the 

 surface of the body being generally smooth *. 



That which Risso first named Calypso, and subsequently Janira, 

 in the opinion of Desmarest, — Consider., p. 192, does not differ from 

 Galathea. 



PORCELLANA, Lam. 



The Porcellanse form a singular cxce})tion among the Macroura, 

 with respect to their tail, which is doubled under as in the Brachyura. 

 They arc otherwise removed from the Galathea by the more ab- 

 breviated, suborbicular, or almost square form of tlieir thorax ; by 

 the mediate antennae, wliich are sunk in their fossulye, by their tri- 

 angular forceps ; and finally, by the internal dilatation of tlie inferior 

 joints of their external foot-jaws. Tlieir body is very flat. 



They are small, slowly-moving Crustacea, found in every sea, 

 and conceal themselves under stones near the shore. 



Doctor Leach has formed a genus with certain species — hexapus 

 Latr., — longicornis. Id., — Bluteli, Risso, Crust., I, 7, &c., which he 

 calls PisiDiA. According to Desmarest, however, it does not differ 

 in any appreciable character. 



Some of them are remarkable for their extremely large and pilose 

 or ciliated forceps. Such are, 1. The Porcellane larrjes pinces ; Can- 

 cer plahjcheles, Pemi., Brit. Zool., IV, vi, 12; Herbst., XLVII, 2, 

 where only the external margin of the forceps is pilose and the nearly 

 naked thorax is rounded; it is found on the rocks in the seas of 

 Europe. 2. The P. hirta. Lam., the whole superior surface of 

 whose forceps and thorax is pilose, and where the latter is nearly 

 oval and becomes thinner anteriorly. It was brought from King's 

 Island by Messrs, Peron and Lesueur. 



The forceps of the others are glabrous. Such is the Cancer hex- 

 apus, L. ; Herbst. XLV^II, 4. The thorax is marked with short, 

 transverse, and slightly ciliated lines : the front trifid, with its middle 

 tooth finally notched. The claws are covered with little blood-red 

 scales and granules, tlie fingers separated and Avithout internal den- 

 tations. It inhabits European seas f . 



The genus Monolkpis , Say, — Journ. of the Acad, of Nat. Sc. of 

 Philad., I, 155; Desmar., Consid., p. 199 and 200, appears to con- 

 stitute the passage from the Porcellanae to the Megalopes. It ap- 

 proaches the first in the two posterior feet, and in the direction of the 

 tail. But this tail has but six segments, and the eyes are very large 



* ^(7?^e Zissf, Desmar., Consider., .xxxiii, 2; Latr., Encyclop. Method., Atl., 

 d'llist. Nat. cccviii, 2. 



t See the article Porcellane, Nouv. Diet. d'HJst. Nat., Ed., II. ; aud Desmar., 

 Consid. sur les Crust., p. 192 — 199. 



